The present invention relates to an apparatus, such as an optical apparatus including binoculars, a camera including a digital camera and a video camera, and the like, and particularly relates to a drive mechanism, for example, for driving a lens and to a guide mechanism, for example, for guiding the lens, with which the apparatus is provided.
In the field of digital cameras, a more downsized (i.e. miniaturized) and compact camera is desired in contrast with a conventional common camera. Meanwhile, as a drive mechanism for driving a lens used in the digital camera, there has been employed a cam mechanism as has been conventionally used in a common camera. That is, the digital camera has a construction in which a pin is fixed to a lens frame (or a movable frame), and in which a plurality of cam slots, engaging the same pin, are formed in a plurality of cylindrical members that engage and overlap one over the other. With the construction, a lens supported by the lens frame is driven in its optical axis.
However, even if one tries to downsize or miniaturize the cylindrical member having the cam slot and/or to downsize the pin engaging the cam slot, etc., there is a limitation to downsizing those components from a point of view of processing and/or assembling it. In other words, there arises a problem that the miniaturization of the cam mechanism can not catch up with the miniaturization of an optical system used therein.
Also, the cam mechanism is equipped with a tilt prevention mechanism for preventing a tilt of each lens advancing and retreating in its optical axis. With this arrangement, the movable frame for holding the lens advances and retreats while turning about the optical axis. Therefore, in case that one tries to miniaturize it while realizing a prevention of mutual interference of the plurality of movable frames, it is difficult to let a span of the tilt prevention mechanism be longer. As a result, a prevention of the tilt of the lens becomes difficult.
Furthermore, in the conventional cam mechanism, each lens is accommodated inside the cylindrical member. Therefore, it is difficult to perform the alignment of the optical system after assemblage thereof.
On the other hand, conventionally, a camera, video camera, digital camera, or the like, has had a guide mechanism for guiding a lens in a direction of an optical axis thereof at a time of moving the lens for zooming, focussing, etc. upon photographing. In the construction, there has been conventionally provided, for example, an MR (magnetic resistance) sensor for detecting a position of the lens that is driven in the optical direction, in order to control the position thereof. This MR sensor is a magnetic sensor, which is a magneto-resistive sensor having a characteristic that its resistance varies in a magnetic field when the intensity of the magnetic field varies. That is, the MR sensor moves in a longitudinal direction nearby a magnetized plate in which there are arranged a plurality of N- and S-poles alternately, with which arrangement the position of an object connected to the MR sensor is detected by reading the state of the magnetic field.
In this construction, in order to enhance an ability of the detection, it is necessary to ensure an accuracy of mutual location and mutual structures between the MR sensor and its counterpart magnetized plate. In this construction, a gap between a sensor surface of the MR sensor and the magnetized plate opposing the sensor surface thereof must be most strictly taken care of in order to ensure the accuracy thereof. However, the MR sensor and the magnetized plate are mounted on separated members moving relative to each other. Therefore, generally speaking, it is difficult to ensure the accuracy of the gap therebetween, only by the accuracy of components employed in the structure and/or by the accuracy of assemblage thereof.
In order to solve this technical problem, it has been practiced that, for example, a spacer or the like having a thickness corresponding to a required gap therebetween is inserted between the MR sensor and the magnetized plate, and that one of the MR sensor and the magnetized plate is brought into a press contact with the other thereof by means of a plate spring, or the like, by which the accuracy of the gap is ensured.
Meanwhile, in a type where the lens frame is hung down by a guide shaft, the lens frame is driven along the guide shaft in the direction of the optical axis. In this arrangement, however, it is necessary to restrict or prevent the turning of the lens frame around the guide shaft. In order to prevent the turning thereof, it has been practiced that an additional guide shaft is provided parallel to the foregoing guide shaft in which the additional guide shaft is fitted to a groove, or the like, that is additionally provided on the lens frame.
In this construction, in case that the optical performance thereof is considerably degraded due to swinging of the center of the optical axis of the lens frame, it is necessary to further suppress the play or looseness between the groove of the lens frame and the additional guide shaft, and the lens frame is biased on one side relative to the additional guide shaft by means of a spring, etc.
However, in the above construction, there are installed the detector for detecting the position of the lens and the mechanism for restricting or preventing the turning of the lens separately, in the guide mechanism for guiding the lens. This leads to an increment of the number of component parts and the number of assembling steps, which in turn incurs a large-sized apparatus and/or a high cost of production.
On the other hand, there has been conventionally provided, for example, a drive mechanism employing a piezoelectric element. The drive mechanism has a plurality of driving parts for linearly driving a plurality of lenses, for instance. With reference to FIG. 25 illustrating a drive mechanism for driving a lens in a camera, it is explained about the drive mechanism.
FIG. 25 is a perspective view of the drive mechanism for driving the lens. The lens drive mechanism has a lens frame 321a for holding a lens 300L1; a shaft bearing part 333a connected to the lens frame 321a; a guide shaft 328a, extending in a direction of the optical axis, slidably engaging the shaft bearing part 333a for guiding the lens frame 321a in the direction thereof; a lens frame 321b for holding a lens 300L2; a shaft bearing part 333b connected to the lens frame 321b; a guide shaft 328b, extending in the direction of the optical axis, slidably engaging the shaft bearing part 333b for guiding the lens frame 321b in the direction thereof.
The guide shaft 328a is held near a front end portion and a rear end portion of the guide shaft 328a by a hole portion 330a formed on a front wall 330f of a stationary frame 330 and by a hole portion 330axe2x80x2 formed on a middle wall 330m of the stationary member 330, so that the front end portion and the rear end portion of the guide shaft 328a slidably engage the stationary frame 330.
In the same way, the guide shaft 328b is held near a front end portion and a rear end portion of the guide shaft 328b hole portion 330b formed on the front wall 330f of the stationary frame 330 and by a hole portion 330bxe2x80x2 (unshown in the figure) formed on the middle wall 330m of the stationary member 330, so that the front end portion and the rear end portion of the guide shaft 328b slidably engage the stationary frame 330.
Each of the shaft bearing parts 333a, 333b is equipped with a plate-spring-like holding plate 331a, 331b which is mounted thereto respectively with a screw (the holding plate 331b is hidden in the figure). The holding plates 331a, 331b make press connect with the guide shafts 328a, 328b, respectively. Therefore, when the lens frames 321a, 321b move on the guide shafts 328a, 328b, the shaft bearing parts 333a, 333b are slid thereon frictionally.
As shown in FIG. 25, the drive mechanism also has a pair of piezoelectric elements 325a, 325b that are mounted to the rear end portions of the guide shafts 328a, 328b. Rear end portions of the piezoelectric elements 325a, 325b are connected to fixing members 332a, 332b, respectively. These fixing members 332a, 332b are fixed to a rear end surface 330c of the stationary frame 330.
The principle of operation of a drive mechanism employing a piezoelectric element is briefly explained below with reference to schematic views shown in FIGS. 26(A), 26(B), 26(C).
As shown in FIG. 26(A), a driving shaft 353 is fixed to one end of a piezoelectric element 352, a fixing member 351 is fixed to the other end of the piezoelectric element 352, and a moving body 354 to be moved is held relative to the driving shaft 353 by a frictional force exerted by a spring for instance. The mass of the fixing member 351 is sufficiently large as compared with the mass of the moving body 354.
When a predetermined voltage is applied to the piezoelectric element 352, the piezoelectric element 352 is inhibited from expanding toward the fixing member 351 due to the force of inertia of the fixing member 351. Therefore the piezoelectric element 352 expands toward the driving shaft 353, causing the driving shaft 353 to be moved leftward in the figure.
In this operation, when the applied voltage is on a gentle rise as shown by part xe2x80x9cA1xe2x80x9d part in FIG. 27, the moving body 354 moves together with the driving shaft 353 by a distance x because the frictional force exerting between the moving body 354 and the driving shaft 353 is larger than the force of inertia of the moving body 354, as shown in FIG. 26(B).
Next, when a voltage of an abrupt fall as shown by part xe2x80x9cB1xe2x80x9d part in FIG. 27 is applied to the piezoelectric element 352, the force of inertia of the moving body 354 is larger than the frictional force exerting therebetween, while the piezoelectric element 352 is contracted. Therefore, at this time, the moving body 354 remains stationary, while only the driving shaft 353 contracts back to its original length so that it moves back by the same distance xe2x80x9cxxe2x80x9d to the original position, as shown in FIG. 26(C).
Applying a voltage with a sawtooth-shaped pulse waveform to the piezoelectric element 352 so that the aforementioned operation is repeated, allows the moving of body 354 to a desired position. By the way, in order to move the moving body 354 in a reverse direction, a voltage having an abrupt rise and a gentle fall is applied to the piezoelectric element 352.
The drive mechanism, as shown in FIG. 25, is actuated on a basis of the same principle of operation. That is, when a voltage with a predetermined sawtooth-shaped pulse waveform is applied repeatedly to the piezoelectric elements 325a, 325b for a specified time, the piezoelectric elements 325a, 325b expands and contracts so that the lens 300L1, 300L2 is moved toward a desired position, under a relation between the frictional force exerting between the guide shaft 328a, 328b and the holding plate 331a, 331b, and the force of inertia due to the mass of both the lens 300L1, 300L2 and the lens frame 321a, 321b. 
However, in case that the drive mechanism is miniaturized with the miniaturization of the camera main body, the mass of the fixing member 332a, 332b is reduced; therefore, the force of inertia is also reduced. This may cause the fixing member 332a, 332b to move against the expansion and contraction of the piezoelectric elements 325a, 325b. That is, in case that the stationary frame 330 is made of an elastically deformable material such as plastic, the rear end surface 330c becomes easily flexible, so that this rear end surface 330c accompanies the movement of the fixing members 332a, 332b. In other words, in case that the stationary frame 330 is made of such an elastically deformable material, the rear end surface 330c has not enough rigidity not to allow the fixing member 332a, 332b to move.
Accordingly, it is an object of the present invention to provide an apparatus having a drive mechanism for driving a moving body in a predetermined direction relative to a stationary member which remains stationary with respect to a body of the apparatus, in which a miniaturization of the drive mechanism is realized, it is easy to make an access to the moving body after assembling the apparatus, and also it is possible to assure a longer span thereof for preventing a tilt of the moving body relative to the predetermined direction.
It is another object of the present invention to provide an apparatus having a guide mechanism for guiding a moving body, in which the guide mechanism has a function to detect the location of the moving body relative to the guide member, to prevent a rotation of the moving body about the guide member, and to remove a play or looseness between the moving body and the guide member, and in which it is possible to reduce the number of assembling parts of the guide mechanism and the number of its assembling steps, in order to realize a miniaturization of the guide mechanism and to realize a low cost of production.
It is still another object of the present invention to provide an apparatus having a drive mechanism for driving a plurality of moving bodies relative to a stationary member which is fixed to a frame, in which each of the moving bodies is moved stably.
In accomplishing these and other objects of the present invention, according to one aspect thereof, there is provided an apparatus comprising: a body; a moving body that is movable in a predetermined direction relative to the body; a stationary member that remains stationary relative to the body and that extends in the predetermined direction; and a plate-like member that is connected to the moving body and that is slidable relative to the stationary member in the predetermined direction with a surface of the plate-like member contacting a surface of the stationary member.
The apparatus may be an optical apparatus including a camera, or may be other apparatus that are used in technical fields different from the optical field.
For example, in case that the apparatus is the camera, the moving body may be a lens frame for holding a lens or lens group, and the predetermined direction may be a direction of an optical axis of the lens or the lens group. In the arrangement, there is no need of a plurality of cylindrical members which overlap one over the other like those employed in the conventional camera as mentioned above; therefore, a diameter of a lens accommodating part does not exceed a diameter of the lens frame. Namely, the miniaturization of the drive mechanism with the moving body is realized. Also, in the arrangement, a lens is not covered with such conventional cylindrical members one over the other; therefore, it is easy to make the access to the lens or lens group as the moving body after the assemblage of the apparatus, and it is easy to align a center of the lens or lens group as the moving body relative to the optical axis. Further, for example, in case that a plurality of lenses or lens groups as the moving bodies are provided so as to move respectively in the optical axis, the lenses or lens groups are fixed to a plurality of plate-like members, respectively, and the plurality of the plate-like members are provided offset from each other in a direction perpendicular to the optical direction, for example. With the arrangement, the plurality of loci of the moving bodies does not interfere with each other; therefore, it is possible to assure respective longer spans thereof enough to prevent the tilt of the moving bodies relative to the optical axis.
According to another aspect of the present invention, there is provided an apparatus comprising: a moving body; a guide member that guides the moving body in a direction in which the guide member extends and that makes a position, or posture, of the moving body stable at a desired location in the direction; an MR sensor that detects the desired location of the moving body in the direction; a magnetized member that cooperates with the MR sensor to detect the desired location of the moving body in the direction; and a biasing member that biases the moving body toward the guide member and that biases the MR sensor toward the magnetized member.
The apparatus may be an optical apparatus including a camera, or may be other apparatus that are used in technical fields different from the optical field.
For example, in case that the apparatus is the camera, the moving body may be a lens frame for holding a lens or lens group. According to the arrangement, the guide mechanism has a function to detect the location of the moving body relative to the guide member by a cooperation of the MR sensor and the magnetized member; the guide mechanism has a function to prevent a rotation of the moving body about the guide member because the guide member makes the position, or posture, of the moving body stable at the desired location in the direction; and the guide mechanism has a function to remove the play or looseness between the moving body and the guide member because the moving body is biased against the guide member by the biasing force exerted by the biasing member. Also, according to the arrangement, it is possible to reduce the number of assembling parts of the guide mechanism and the number of its assembling steps, because there is no need of providing separate members for detecting the position of the moving body relative to the guide member and for preventing or regulating the rotation of the moving body about the guide member, unlike the aforementioned conventional art. With the simple arrangement, the miniaturization of the guide mechanism and the low cost of production thereof are realized.
According to still another aspect of the present invention, there is provided an apparatus comprising: a frame; a stationary member that is fixed to the frame; a plurality of electromechanical transducers each of which has a pair of ends, in which one of the ends of each of the electromechanical transducers is fixed to the stationary member, and in which the other of the ends thereof expands and contracts with respect to the stationary member; a plurality of drive members each of which is fixed to the other of the ends of each of the electromechanical transducers; and a plurality of moving bodies each of which frictionally engages one of the drive members.
The apparatus may be an optical apparatus including a camera, or may be other apparatus that are used in technical fields different from the optical field.
For example, in case that the apparatus is the camera, the moving body may be a lens frame for holding a lens or lens group.
According to the arrangement, for example, each drive member reciprocates in response to the expansion and contraction of each of the electromechanical transducers. At this time, in compliance with a voltage with, for example, a waveform having a rapid rise and a gentle fall, each moving body is driven along the drive member. In the operation, there is provided a common stationary member for the plurality of electromechanical transducers and the plurality of drive members. Namely, the common stationary member has a large mass. Therefore, each of the drive members reciprocates without loss of the amount of the reciprocation, so that the moving body is driven stably. Thus, even if the drive mechanism is downsized or miniaturized, a precision of positioning the moving body relative to the frame or the stationary member is not deteriorated.